Allright ! I received the missing 8255AC chip for this XT board :

It's in good shape, but it's also quite nasty. I've attempted to fired it up, but it does nothing ... 🙁
Also the chip I received looks fake (it feels different on the top vs the bottom and scrubbing it with a q-tip with alcohol made the q-tip to turn black a little), but I'm sure it would work anyways.

Now the board still didn't work, but I noticed something when I inserted my POST card (yeah I know they don't work in XT, but the codes are not important here) : the reset line is constantly set to high. So it can't work if it's always set to high! which makes me think something somewhere must be wrong on the reset line ... Now I have to find it ...

DataExpert EXP8049

Hello there ! I haven't updated this topic in a while ...

First thing first : @Kassiny very nice ! Can you send me your BIOS rom ? 😁

And now some good news about the Turbo XT motherboard :
I've tried to use the landmark/supersoft diagnostic rom (http://www.minuszerodegrees.net/supersoft_lan … dmark%20ROM.htm) but it still didn't work, which is weird because that thing truely works even with really broken boards. But I paid closer attention to the board and noticed something ...
Look on the old photo, on the left of the 5th ISA slot starting from the top of the picture ... See that spot with "14.318" written ? Yes that's the 14.318MHz crystal missing, I can imagine why it doesn't work now 🤣

After salvaging a 14.318MHz crystal from a dead 486 motherboard, here's the finished job :

And what a surprise, now it works 😁

What a weird BIOS though. After a key press, it asks me to insert a floppy disk in the drive A, but sadly I haven't been able to get the floppy disk drive to work ... But maybe that's just a dip switch setting ... which I don't know because I don't know which board that is, and also, the dip switches look like this at the moment :

I think I'll just swap them with a brand new one 😅

And for those that would want to try it, here's the BIOS :

Here's a bonus information ; I've found the ad for the computer in which that XT board was and ... ugh judge it by yourself 🤣

Furthermore, this computer was made far away in the south of France, but I live far away in the north, I wonder how/why it arrived here x) (and for your information, people tend to leave the north for the south rather than the opposite).
That's a cool little mystery about this machine 😁

FYI on the XT the reset line is controlled by 8284 clock generator chip, among other things it also provides a well timed reset pulse for the system. So with the 14.318MHz crystal missing there is no clock, 8284 is not working and reset is driven low permanently.
As for your other mobo woes, maybe there isn't a broken trace that you're looking for. All that spill has badly corroded many of the soldered connection nearby, I can tell from the photo. You probably need to rework all of those, and it's not an easy job - the "bad" solder is difficult to remove. But you don't have to get it all out, just most of it and replace it with a fresh one. Inspect all nearby vias as well, test with the meter, perhaps one or more is damaged and will need a thin wire fix.

You mean for the PCChips ?
Yeah that's what I'm going to do I guess. However I haven't found any bad via, but some may be on the verge of dying and give "false negatives" ? That would explain why the board is working at first then the KBC doesn't work anymore.